A conventional AWD driveline for a motor vehicle may include a primary front drive axle coupled to a secondary or auxiliary rear drive axle. When the driveline is operating in a 4×2 mode of operation (i.e., four wheels, with two of them operating as driving wheels), the primary front drive axle must provide tractive forces not only to keep the motor vehicle moving, but also to overcome the frictional losses of the secondary or auxiliary rear drive axle that is being driven through the tire/road surface interface. Driveline losses may be due to oil churning losses, viscous drag, inertia, as well as friction.
In an effort to minimize loss and provide a more fuel efficient driveline when in a 4×2 mode of operation to improve overall fuel economy, it may be desirable to disconnect the secondary or auxiliary drive system, including the secondary or auxiliary rear drive axle and the rear wheels. Wheel hub disconnects generally may be separate from the rear differential housing and positioned close to each wheel, may be integrated into the rear differential housing, or may be somewhere in between the wheel and the rear differential housing. Accordingly, disconnecting the rear wheels may be accomplished at the ends of the wheels or at the output of a rear drive module (RDM).
A system that disconnects the rear wheels at the ends of the wheels may be more conventional and/or typical in motor vehicles, but may also be more complicated than a system that disconnects the wheels at the RDM. While a system that disconnects the wheels at the RDM may be acceptable since most of the system losses are internal to the RDM, such a system may undesirably increase the package size and component count of the wheel disconnect system. It may be desirable to provide a wheel disconnect system that disconnects the wheels at the output of the rear drive module, while managing to avoid an increased package size and component count.